Excluding nonmelanoma skin cancers, prostate cancer is the most common cancer afflicting American men. The American Cancer Society estimates that over 180,00 new cases will be diagnosed in the U.S. in the year 2000 alone, and that nearly 32,000 people will die from the disease. Prostate cancer is second only to lung cancer as the leading cause of cancer death in men, accounting for roughly 11%.
Prostate cancer is defined as malignant tumor growth within the prostate gland. Its cause is unknown, although high dietary fat intake and increased testosterone levels are believed to be contributory factors. A letter scale (“A” through “D”), which accounts for the location of the cancer, is commonly used to classify the stage of disease. In Stage A, the tumor is not palpable but is detectable in microscopic biopsy. Stage B is characterized by a palpable tumor confined to the prostate. By Stage C, the tumor extends locally beyond the prostate with no distant metastasis. By Stage D, cancer has spread to the regional lymph nodes or has produced distant metastasis.
In the early stages, prostate cancer is most commonly treated by prostate removal or by brachytherapy. More advanced cases are treated by medical hormonal manipulation or orchiectomy to reduce testosterone levels and curb spreading of the disease, by chemotherapy, or by external beam radiation therapy.
With regard to treatment of early stage prostate cancer, the state of the art has several drawbacks. Radical prostatectomy is often recommended for treatment of localized stage A and B prostate cancers. Under general or spinal anesthesia, an incision is made through a patient's abdomen or perineal area, and the diseased prostate is removed. The procedure is lengthy, especially if a lymph node dissection is simultaneously performed, and requires a hospital stay of 2-5 days. Possible complications include impotence and urinary incontinence.
Internal radiation therapy or brachytherapy has recently been modified and holds great promise for the treatment of early stage prostate cancer. Radioactive pellets or seeds of, for example, iodine-125, gold-198, palladium-103, ytterbium-169, or iridium-192, are deposited directly into the prostate through needle placement. Imaging tests, such as transrectal ultrasound, CT scans, or MRI, are used to accurately guide placement of the radioactive material. Advantageously, radiation is administered directly to the prostate with less damage to surrounding tissues, requiring a significantly smaller radiation dosage as compared to external beam radiation therapy. Furthermore, the procedure need only be performed once. Complications include a lower, yet still significant, incidence of impotence and urinary incontinence, compared to prostate removal procedures.
The radioactive seeds are placed inside thin needles, which are inserted through the skin of the perineum (area between the scrotum and anus) into the prostate. Each needle is slowly retracted with a spinning motion by a first practitioner while a plunger within the needle, and proximal of the radioactive seeds, is held stationary by a second practitioner. The plunger keeps the seeds in place during retraction of the needle, while rotation of the needle during retraction prevents jamming of the seeds while delivering the seeds in a line within the prostate.
The seeds, which are permanently implanted, give off radiation for weeks or months. Their presence causes little discomfort, and they are left in the prostate after decay of the radioactivity. For about a week following needle insertion, patients may experience pain in the perineal area, and urine may have a red-brown discoloration.
Current surgical apparatus and methods for loading the seeds into the brachytherapy needles prior to delivery are both hazardous and inefficient. Medical personnel hand-load the seeds in an alternating arrangement of seeds and spacers, thereby unnecessarily subjecting the personnel to radiation exposure. Minute seed size (e.g., 5 mm in length) compounds the problem by making the procedure slow and meticulous. Furthermore, the seeds accidentally may be dropped or misplaced during loading, thereby increasing exposure risk. Also, the seed loader may make a mistake in the packing order of seeds and spacers, potentially leading to “hot spots” and “cold spots” within a patient's prostate where the tissue is subjected to incorrect radiation dosages. Finally, the types and total number of seeds and needles used must be individualized for each patient depending on the size of the prostate and the Gleason score of the cancer, thereby increasing opportunity for error.
Attempts have been made to address various aspects of these concerns. For example, U.S. Pat. No. 4,815,449 to Horowitz describes an absorbable member with seeds spaced within the member to facilitate proper spacing during delivery. The absorbable member may be pre-formed for easy loading. While pre-forming may effectively decrease the complexity and time required to load the needles, it also impedes the physician's ability to tailor the seed spacing to a specific patient's needs. Furthermore, these absorbable members have been prone to jamming within the needle in clinical use.
U.S. Pat. No. 5,928,130 to Schmidt provides a sleeve, pre-loaded with seeds and spacers at a remote site, which may be inserted through the needle lumen. Seeds then are implanted using conventional techniques. As with the Horowitz device, the physician's ability to tailor seed spacing is limited. Furthermore, the method of loading seeds into the sleeve at the remote site is not disclosed, and presumably involves technicians at the loading site being exposed to radiation.
PCT publication WO 99/20337 to Rydell describes a gun-like radioactive seed implantation device that strips seeds one by one from a cartridge and advances them to the implantation site. The Rydell device has several drawbacks. The device is rather large and may prove intrusive in the surgical field. It increases the time required to perform surgery since seeds only may be delivered one at a time. The device also is mechanically complex and may be subject to malfunction. Finally, there is only one cartridge from which the device draws implantable materials. Thus, a packing arrangement of seeds and spacers tailored for a specific patient requires pre-loading of the cartridge, again exposing the loader to radiation.
While each of these devices may provide some benefit over the previously known apparatus and methods, none satisfactorily addresses the shortcomings of current loading techniques. In view of these drawbacks, it would be desirable to provide methods and apparatus that allow rapid seed loading.
It further would be desirable to provide methods and apparatus for brachytherapy seed loading that minimize radiation exposure of attendant medical personnel.
It also would be desirable to provide methods and apparatus that may be used in conjunction with standard brachytherapy needles.
It further would be desirable to provide methods and apparatus that allow tailoring of the packing arrangement of seeds and spacers to meet the needs of a specific patient.